The world's smallest Vacuum tube TV bar generator ?

[Kevin Kuehn]

Could be it's nothing more than a audio frequency(vertical) and a RF freq generator(horizontal) that beats against the sets scanning oscillator frequencies. That neon lamp on the front may even be used as the trigger in a saw tooth relaxation type oscillator. I've done the same using my function generator and it actually works very well for linearity adjustments. Be aware that such a simple piece as you have there likely does not use an AC line isolation transformer. It would be very wise to have the set under test powered through an isolation transformer.